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In the last few years a new method for surface preparation has evolved, namely thermo-abrasive blasting. This technique utilises a high enthalpy thermal jet to propel abrasive particles. The thermo-abrasive blasting gun, also called a thermal gun, is based on the principles of High Velocity Air Fuel (HVAF) processes. Nozzles used for thermo-abrasive blasting are subjected to thermal loading, wear and mechanical stresses. Therefore, the nozzle geometry and materials are critical for reliable performance of a thermo-abrasive system. In this investigation, the thermal stresses developed in the nozzle materials for thermo-abrasive blasting were analysed. The analytical and the computational models of the thermo-abrasive gun and the nozzle were developed. The computational fluid dynamics, thermal and structural finite element analyses have been employed in this study. The nozzle materials investigated were tungsten carbide, hot pressed silicon carbide, nitride-bonded cast silicon carbide and SIALON. The simulation and experimental results show that the highest thermal stresses occur during the first two minutes from the start of the thermal gun. However, thermal stresses are also high after the system is shut off. The nozzle geometry was optimised, which provided high cleaning rates with evidence of improved thermal loading, based on the experimental results. A new design of the thermal gun and the ignition method associated with a HVAF system were developed in this study. It is also concluded that the computation fluid dynamic and the finite element technique can be used to optimise the design of thermo-abrasive blasting nozzles. / Thesis (Ph.D. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2004.

This thesis is a study of impinging jet PV/Thermal collectors. More specifically, the thesis deals with the development of a model for this type of collector and its validation. The model developed for this thesis consists of a series of energy balances at every layer of the collector. The transient effects due to thermal mass of the different layers were taken into account. The resulting differential equations were solved using the backwards Euler method in an iterative manner. The validation of the model was done using a prototype of the collector. The aperture area of the collector was 0.78m2 and the PV cells covered 0.27m2. The collector was tested on 8 different days between January 30th and March 31st 2010. The experiments were conducted with various weather conditions, and parameters (such as mass flow rate and inlet temperature). The data was taken every 0.5 seconds and averaged over 5 minutes. In general, the model was found to work very well. For March 31st, the total modeled heat gain for the day was found to be within 2.1% of the experimental data. The PV electrical energy was found to be within 4.4% of the experimental results. The model was also found to work well with longer time steps than 5 minutes. Furthermore, the model seemed to work relatively well without accounting for the transient effects due to thermal mass.

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A laboratory study was conducted to assess the relationship between degree of volatile organic compound (VOC) mass removal from soil and heating duration, initial dense non-aqueous phase liquid (DNAPL) saturation, and grain size. The relationship between post-remedy sampling temperature and VOC soil concentration was examined. Soil contained in glass jars was spiked with DNAPL phase tetrachloroethylene (PCE), saturated, and placed in an oven for a specified period of time. The soil temperature at the centre of each jar was monitored during heating. Upon removal from the oven, each jar was immediately capped with an air tight seal and placed into an ice bath until the soil temperature had cooled to the desired sampling temperature. The jar caps were subsequently removed and the soil was sampled using a coring tool and immersed into pre-weighed vials containing methanol. PCE in soil samples was quantified using purge-and-trap with gas chromatography/mass spectrometry. Soil temperature increased steadily from ambient until reaching a plateau at 89 ºC ± 4 ºC due to co-boiling of DNAPL phase PCE and water. A linear relationship was found between the length of the co-boiling plateau and the initial PCE saturation. Co-boiling continued until DNAPL phase PCE had been depleted, at which time the soil temperature increased to the boiling point of water and remained constant while remaining pore water was removed. PCE soil concentrations decreased rapidly in the early stages of heating, but leveled off between 9.0 and 19 ppb soon after the soil became dried out. Analysis of the sensitivity to initial PCE saturation data revealed that the concentration of PCE in post-remedy samples increased with increasing initial saturation. Results of the sensitivity to grain size tests showed a decreasing trend between PCE soil concentration and decreasing sand grain size while temperature at sampling was not found to affect the amount of PCE quantified post-thermal remedy. Soil temperature at the centre of each jar during cooling was measured and an analytical solution was fit to the recorded data. From this data, the thermal diffusivity of the soil was approximated and was found to range from 1.4 x 10-7 to 1.8 x 10-7 m2/s. / Thesis (Master, Civil Engineering) -- Queen's University, 2007-12-11 10:12:50.564

An integrated circuit can now contain more than one billion transistors. With increasing system integration and technology scaling, power and power-related issues have become the primary challenges of integrated circuit design. In this dissertation, techniques and algorithms, from system-level synthesis to emerging integration and device technologies, are proposed to address the power and power-induced thermal and reliability challenges of modern billion-transistor integrated circuit design. In Chapter 1, the challenges of semiconductor technology scaling are introduced. Chapter 2 reviews the related works. Chapter 3 focuses on the reliability optimization issue during system-level design. A reliable application-specic multiprocessor system-on-chip synthesis system is proposed, called TASR, which exploits redundancy and thermal-aware design planning to produce reliable and compact circuit designs. Chapter 4 introduces three-dimensional (3D) integration, a new integrated circuit fabrication and integration technology. Thermal issue is a primary concern of 3D integration. A 3D integrated circuit heat flow analytical framework is proposed in this chapter. Proactive, continuously-engaged hardware and operating system thermal management techniques are presented and evaluated which optimize system performance than state-of-the-art techniques while honoring the same temperature bound. Chapter 5 presents reconfigurable architecture design using single-electron tunneling transistor, an ultra-low-power nanometer-scale device. The proposed design has the potential to overcome the power and energy barriers for both high-performance computing and ultra-low-power embedded systems. Conclusions are drawn in Chapter 6. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2009-07-02 19:24:18.632